void CreatPolyn(Polynomial &P, int m){
    P = new PNode;
    P->next = NULL;
    while(m--){
        PNode *q = new PNode;
        cin >> q->coef >> q->expn;
        q->next = P->next;
        P->next = q;
    }
    for(PNode *i = P->next; i; i = i->next){
        for(PNode *j = i->next; j; j = j->next){
            if(i->expn > j->expn){
                swap(i->expn, j->expn);
                swap(i->coef, j->coef);
            }
        }
    }
}